This invention relates to color picture tubes of the type having a shadow mask attached to a peripheral frame, which is suspended in relation to a cathodoluminescent screen, and particularly to novel means for reducing microphonic vibrations in the shadow mask.
In these color picture tubes, the accuracy with which the electron beams, emitted from an electron gun, strike individual elemental cathodoluminescent screen areas depends, to a great degree, upon the accuracy with which the shadow mask apertures are aligned with the elemental screen areas during operation of the tube. Although vibration of the shadow mask relative to the elemental screen areas is generally undesirable, tube performance becomes greatly deteriorated when the frequency of mask vibration beats with the electron beam scanning frequency.
The present invention changes the resonant frequency of the mask to eliminate or greatly reduce any vibration beat with the scanning frequency.